Weighting By Age

I was recently asked why we don’t include the GWU/Battleground tracking poll in our tracking poll average. There are two reasons for this:

This tracker is not really a daily tracker in the sense that it does not sample every day.
This tracker is showing very different results compared to the other trackers, and it looks to have some fundamental methodological problems.

Now, thanks to Nate Silver at 538, I know why this poll is so out of whack with the other trackers–they don’t weight by age. Nate looks at the numbers and finds that this skews their internals heavily towards older voters. While weighting by age may not have been necessary ten or twenty years ago, because of the cell phone effect and a wide disparity in voting preferences between younger and older voters in this election cycle, weighting by age is absolutely necessary in 2008.